Inhibition of peroxide formation in



JED'STATES PATENT OFFICE INHIBITION OF PEROXIDE FORMATION IN *ALIPHATIC IETHERS Theodore Evans, Berkeley, Calif., assignor to shell Development Company, San Francisco, Califl, a. corporation of Delaware No, Drawing. Original application August 19, 1936, Serial No, 96,816. Divided and this appli-,

cationMay 3;1838; Serial No. 205,755

l Claims. ((123-250) 'riu -1nvent1on relates tothe stabilization of one or more aliphatic mixed ethers and/or one llphatic ethers and it morepartlcularly relates or more aliphatic symmetrical isoethers. These 8. method of inhibiting the formation of 10x stabilized compositions may-be stored for relativeve ii'npurities, as peroxides I in aliphatic ly long periods of time and they may be shipped rs 'particularly aliphatic mixed and aliphatic for great distances, in the conventional conymm tricalisoethers. The invention also ,retainers, without substantial peroxide formation or ates to"stahilized compositions consisting of or deterioration of the ether content of the comoniprising" aliphatic mixed and aliphatic symposition. The stabilized compositions are useful I Ythers. I for a wide variety of purposes, andthey are lil'iatidfthers, particularly the mixed useful as raw materials in the production of a m he and symmetrical isoethers, when stored wide variety of products. nderordinaryfstorage conditionseven in glass The process of my invention comprises incors,' u"n'dergof considerable deterioration porating with the ether to be stabilized, or with h'etheriswntamlnated with oxidative the mixture comprising one or more of such ther decomposition products which mateethers, by mixing or any other suitable means, a y iroreaiseits value for many commercial stabilizing amount of an organic carbonylic compurposesflln some'cases, due to their highperpound of the class consisting of ketones and caroidde 'cont'ent, further treatment, asdistillation, boxylic acids. By the term stabilizing amount", v jofj'the stored'ether or ether composition is haz- I mean an amount of an organic carbonylic comugcmu,"

dous. Z'Theetheis on "standing usually detepound or mixture of such compounds effective to rioratebyireactingwith oxygen to form peroxstabilize the ethercontent of the treated matetlesfwh'ich inturn by interaction and/or sponrial against deterioration, for 'examplefagainst t'a'n'eous decomposition may yield other deleterious auto-oxidation resulting in peroxide formation. I purities-the removal of whichis in many cases The ethers stabilized in accordance with the g5 adimcult and costly proceeding. The impurities invention are members of the-class of ethers conformed inthealiphatic mixed ethers andthealisisting of aliphatic mixed ethers and aliphatic 'phatic symmetrical isoethers by spontaneous deymm tri l isoethers- The aliphatic m x teri'dration or auto oxidatlon when such ethers ethers are ethers wherein two different aliphatic j are stored or shipped alone or in admixture with radic ls ar link d o n ther xy n tom. Th "one or more other-materials, may for convenience d ff e t al p t radicals y be S t Cha n 30 rm ioxldativelmpurities, which t m i radicals or branched chain radicals or one may *1fit 'nd d=t emb g peroxides d t c be straightchain and theother branched. The mmgtm fln r ti h t ti of t radicals may be the residues of aliphatic norallphatic mlxed and aliphatic symmetrical iso- 9 hh Secondary alcohols they ethers increaseswith lapse of time and is usually may be the radlchls Fliphahc tertiary alwhols- 35 "favored by: the presence of oxygen in the storage The simplest ahphahc mixed ether is methyl f hjp htgm th presence, as is l, ethyl ether. Other readily available aliphatic of di sbl edtb e m th th as manufacmixed ethers are methyl propyl ether, methyl isotu 33, q t particularly direct propyl ether; methylnormal butyl ether, methyl ,tumi lf vexposure heat; exposure to tertiary butyl ether, methyl amyl ether, methyl 40 *p mum-a su a m secondary amyl ether, methyl tertiary amyl ether, n ofm lnventjo to pmvide a methyl hexyl ether, methyl tertiary hexyl ether, Medical and highly effective method for subethyl Propyl ether, ethyl isopmpyl ether ethyl y g stan'tially inhibiting the formation of peroxides normal hhtyl ether ethyl secondary hutyl ether,

and'other deleterious impurities in the ethers to ethyl ternary hutyl ether ethyl amyl etherethyl 45 l which this invention relates when thesame, either Secondary amyl ether, ethyl tertiary amyl t r, "in' the purestate or in admixture withother mathe hthyl hexyl ethers the PTOPYI butyl s. te'rlalsas hydrocarbons and the like, are stored, the Prowl amyl ethers a the 1ike- The homos i p r u -f r purposes where jastable ether logues, analogues and substitution products of the or ether jContainingmixture substantially free of above, as well as mixed ethers wherein one or both 50 "ge x es 1 de i d, of the aliphatic radicals is/are unsaturated, as

, Itis'anotherobject of my invention to provide for exampleethyl 'isobutenyl h llyl ison oveland 'useful compositions which are substanbutenyl et hyl isopen y ether and the like.

7 'ftially stabilized against deterioration and peroxmay be stabilized in accordance with the invenfiiiideforhrationand which consist of or comprise tion. The aliphatic mixed ethers possessing a methyl group linked to an ether oxygen atom as the methyl butyl ethers, etc. are usually more stable than the higher mixed ethers possessing radicals containing at least two carbon atoms. Under some conditions, the former may be sufllciently stable and may not require stabilization. However, the latter, are very susceptible to autooxidation and must be stabilized if excessive peroxide formation is to be avoided when they are stored for even relatively short periods of time.

In the aliphatic symmetrical isoethers, the allphatic radicals linked to the ether oxygen atom are identical, and the compound forms a chain at least doubly branched. The aliphatic radicals are theradicals of aliphatic isoprlmaryv alcohols, normalor lso-secondary alcohols or tertiary alcohols. The simplest aliphatic symmetrical isoether is diisopropyl ether, which compound is particularly susceptible to auto-oxidation with the formation of peroxides. After standing for a short period of time, diisopropyl ether usually contains sumcient peroxide to render its purification by distllation, without a previous treatment to destroy the peroxide, extremely hazardous due to dangers of explosion.

Other readily available aliphatic symmetrical isoethers are: diisobutyl ether, disecondary butyl ether, ditertiary butyl ether, diisoamyl ether, the disecondary amyl ethers, the ditertiary amyi ethers, diisohexyl ether and the like and their homologues, analogues and substitution products. The aliphatic unsaturated symmetrical isoethers as diisobutenyl ether, diisopentenyl ether, disecondary pentenyl ether and the like may be stabilized in accordance with the invention.

The ether stabilizing agents or peroxide-formation inhibiting agents used in accordance with the invention are carbonylic compounds, particularly carbonylic compounds of the class consisting of the ketones and carboxylic acids. A suitable carbonylic compound of this preferred class may be saturated or unsaturated and it may be of aliphatic, aralkyl or alicyclic character and possess one or aplurality of carbonyl groups.

Suitable representative carbonylic compounds are the following: the ketones as acetone, methyl propyl ketone, methyl ethyl ketone, diethyl ketone, dipropyl ketone, methyl prownyl ketone, acetophenone, benzophenone, benzylideneacetone, benzyiidinacetophenone, diacetyl, acetylv acetone, acetophenoneacetone, pyruvic acid, aceto-aoetic acid, laevruic acid and the 11!..- the monoand polycarboxylic acids as formic, acetic, propionic, butyric, isobutyric, valeric, acrylic, oxalic, malonic, succinic, glutaric, adipic, pimelic, suberic, maleic, fumarlc, tartronic,malic,ric, benzoic, phenyi acetic, the toluic acids, hydrocinnamic, hydratropic, the toyl-acetic acids, the ethyl-benzoic acids, mesitylenic, salicylic, hydroxy-benzoic, anisic, mandelic. tropic, cinnamic, atropic, phenyl-propiolic, ooumaric and the like and their homologues, analogues and suitable substitution products.

Satisfactory results have been obtained when the carbonylic inhibiting agent is used in an amount equal to about 0.004 mol. of inhibitor per liter of ether stabilized. However, the invention is not limited to the use of any specific proportion of the inhibitor. In some cases, the presence of the carbonylic compound in a concentration equal to about 0.001% by weight of the ether content of the material to be stabilized may be effective; in other cases, it may be desirable to use as much as 10% or more oi the stabilizing agent.

The amount of the inhibitor to be used will usually be dependent upon the particular stabilizing agent, upon the particular ether or ether combination to be stabilized and upon the conditions to which the stabilized material will be subjected. In many cases, carbonylic compounds of the class consisting of ketones and carboxylic acids have the desired eifectiveness when employed in concentrations of from about 0.002% to about 2% by weight of the ether content of material stabilized.

If desired, the stabilizing agent employed may comprise a mixture of carbonylic compounds. The carbonylic stabilizing material may be added to the ether or ether-containing material to be stabilized in any desired manner. A carbonylic compound may be added per se or dissolved or suspended in a suitable media. It may be desirable to select the carbonylic stabilizing agent with respect to the ether or ether composition to be stabilized so that the former is soluble to the desired extent in the latter. It may, in some cases, be desirable to select the specific inhibitor material with respect to the material stabilized so that it may, if desired, be subsequently separated therefrom by some convenient means as distillation, extraction, etc. I

The material stabilized may consist of one or more aliphatic ethers of the class consisting of the aliphatic mixed ethers and aliphatic symmetrical isoethers. The invention also embraces within its scope the stabilization against deterioration and peroxide formation of the ether content of mixtures comprising one or more of such ethers in substantial amount. The ether or ethers may be in admixture with one or more solvents or diluents as the following: the aromatic and aralkyl hydrocarbons as benzene, toluene, xylene, cymene, ethyl benzene, etc.; the alicyclic hydrocarbons as cyclohexane, tetrahydrobenzene, etc.; the saturated as well as unsaturated aliphatic hydrocarbons; the hydrocarbon mixtures as gasoline, kerosene, Diesel oil, fuel oil, lubricating oil, etc.; halogenated hydrocarhens; and various oxy compounds as alcohols and be regarded as limited to the specific ethers stabilized nor to the specific carbonylic compounds recited.

Example I Two samples of about the same volume were drawn from afreshiy prepared stock of ethyl tertiary butyl ether and placed in glass sample bottles. One of the samples was left untreated; the other sample was stabilized by the addition thereto of methyl ethyl ketone. The inhibitor was used in an amount corresponding to about 2 c. c. of ketone per liter of ether stabilized. The sample bottles were closed with stoppers provided with capillary tubes to permit the contents of the bottles to have access to the atmosphere, and the bottles stored in a dark cabinet for six months. At the end of this time the contents of the bottles were analyzed to determine the amount of peroxide formed.

The peroxide was determined as follows: 2 c. c.

following table:

of thiosulphate solution is equivalent to 0.00625 mcil. of peroxide oxygen per liter of ether.

The results of the analyses are shown in the C. c. N120 thiosulpbatalzc. ther Titratio after 0 months Ethyl tertiary butyl.. None Do Metbylothylketone.

These results show that while a considerable amount of peroxide was formed in the untreated sample, there was practically no peroxide formed in the treated mp1s.

Example 11 an a- 4 avw. in the lit; acid, the inhibitor was used in an amount corresponding to about 0.004 mol. of the carbonylic compound per liter of ether. Acetone and methyl-ethyl ketone were used in an amount corresponding to about 2 c. c. of the ketone per. liter of ether. The samples. were stored in a dark cabinet for 12 months. At the end of this time the peroxide content or the various samples was determined by the method described in Example I. The results were as salicylic acid injlnhibiting peroxide formation in ethyl tertiary amyi ether stored in metal or glass containers. p

Grams roxide oxygen iter other Samples After 3 Alter 7 months months Stored in tin cans:

ether-no inhibit 0. 32 1.04 a t? 1 1" 0.02 E. 123::

c. c. ether-no inhibitor 1.28 100 e. c. etber+0.05 gm. salicylic acid 0.01

Example .1

' Two samples of 200 c. c. each of the same stock of freshly prepared dllssopropyl ether were placed in tin cans. One of thesamples was stabilized against peroxide formation by the addition there-- to of about 0.1 gm. of salicyclic acid. The other sample was untreated. The cans were closed and stored for three months. At the end of this time the peroxide content of each sample was determined. The untreated sample contained 2.14 gm. of peroxide oxygen per liter of ether, while the stabilized sample was substantially free of peroxide.

Salicylic acid peroxide formation ether stored in glass bottles for a period of 10 months.

While I have described my invention in a detailed manner and provided examples illustrating follows: '1. A composition of matter stabilized against 0 0 W20 thiosulit phate/ 2 c. c other M01118 M peroxide Ether Inhibltor wa Initial Titration titration g 'f g 12 months Ethyl tortiarybutyl..- None 0.10 am 0.01 Do.. A am 2.00 one Do Salicylicocld 0.10 0.35 Do Methyl ethyl ketono-- 0.10 0.7!

It is seen "om the above results all or the carbonylic compounds used were eflective in inhibiting peroxide formation in ethyl tertiary butyl ether.

Example III Two samples of 200 c. c. each of the same stock." of ethyl tertiary amyl ether were placed in tin cans. The contents of one of the cans was stabilized against peroxide formation by theaddition thereto of about 0.10 gm. of salicylic acid. The cans were stoppered and stored for 96 days. At the end of this time the peroxide content of each sample was determined.

The untreated sample contained 0.32 gm. of peroxide oxygen per liter of ether, while the sample to which salicylic acid had been added was found to be free of peroxide.

Example IV peroxide formation which comprises an aliphatic mixed ether and a stabilizing amount of a carbonylic compound selected from the group con 1 sisting of acetone, methyl ethyl ketone and sailethy amountof a car- Q a 1233i other ano. a stabilize Longhocompound animated from unit sisting of acetone, methyl ethyl ketone and salicylic acid.

5. A composition of matter stabilized against peroxide formation which comprises an aliphatic mixed ether of the group consisting of ethyl tertiary butyl ether and ethyl tertiary amyl ether and a stabilizing amount of a carbonylic compound selected from the group consisting of acetone, methyl ethyl ketone and salicylic acid.

6. A composition of matter stabilized against peroxide formation which comprises an aliphatic mixed ether of the group consisting of ethyl tertiary butyl ether and ethyl tertiary amyl ether and a stabilizing amount of salicylic acid.

7. A composition of matter stabilized against -peroxide formation which comprises ethyl tertiary butyl ether and a stabilizing amount of a v carbonylic compound selected from the group 

